The present invention relates generally to plastic fasteners and more particularly to devices used in the dispensing of plastic fasteners.
In U.S. Pat. No. 4,039,078 to A. R. Bone, which is incorporated herein by reference, there are disclosed several different types of plastic fasteners (also commonly referred to in the art as plastic attachments). Each plastic fastener described in the patent is manufactured in an H-shaped configuration, with two shortened parallel cross-bars, or T-bars, being interconnected at their approximate midpoints by a thin, flexible filament which extends orthogonally therebetween. Each type of plastic fastener represented in the patent is shown as being fabricated as part of continuously connected ladder stock. In each instance, the ladder stock is formed from two elongated and continuous plastic side members, or rails, which are coupled together by a plurality of plastic cross links, or filaments, the cross links preferably being equidistantly spaced. The stock may be produced from flexible plastics material including nylon, polypropylene and other similar materials using conventional molding or stamping techniques. Ladder stock of the type described above is presently manufactured and sold by Avery Dennison™ Corporation of Pasadena, Calif. under the Plastic Staple™ and Elastic Staple™ lines of plastic fasteners.
Either manually or with the aid of specifically designed devices, individual fasteners may be severed and dispensed from a supply of ladder stock to couple buttons to fabric, merchandising tags to articles of commerce, or, in general, any two desired articles.
Specifically designed devices for dispensing plastic fasteners are well known in the art. One well-known device for dispensing individual plastic fasteners from a reel of ladder-type fastener stock includes a pair of hollow needles which are adapted to penetrate through a particular item, a feed mechanism for advancing each rail of the supply of ladder stock into axial alignment behind the longitudinal bore defined by a corresponding hollow needle, a severing mechanism for severing a fastener to be dispensed through the pair of hollowed needles from the remainder of the ladder stock, and an ejection mechanism for ejecting the cross-bars of the severed fastener through the bores of the pair of hollowed needles and, in turn, through the particular item which is penetrated by the needles.
For example, in commonly assigned U.S. Pat. No. 5,433,366, which is incorporated herein by reference, there is disclosed a device for dispensing plastic attachments of the type which are formed as part of a roll of continuously connected ladder stock. In one embodiment, the device includes a pair of hollow slotted needles each having a tip, a rear end and a longitudinal axis. A feed wheel, placed proximate to the rear ends of the pair of needles, is used to feed individual attachments of a roll of ladder stock into the pair of needles through their respective rear ends at angles relative to the longitudinal axes thereof. Once inserted into the needles, an attachment is severed from the remainder of the ladder stock by a knife and is then expelled from the needles by a pair of ejector rods movable along the longitudinal axes of the pair of needles. Because attachments are fed into the pair of needles at angles relative to their longitudinal axes, no shuttling of the needles between an attachment feeding position and an attachment ejecting position is required. The pair of needles, the feed wheel, the knife, and the pair of ejector rods are all mounted on a vertically movable head member. An electric motor assembly is used to move the head member between an attachment dispensing position and a withdrawal position. The vertical movement of the head member drives the operation of the feed wheel, the knife and the ejector rods.
Examples of some plastic fastener dispensing devices which are presently available in commerce are manufactured and sold by Avery Dennison™ Corporation of Pasadena, Calif. under the following names: the ST9000™, the Elastic Staple™ Single Needle System (SNS), the Elastic Staple™ Variable Needle System (VNS) and the Elastic Staple™ Single Needle System (SNS) Module.
As noted above, devices for dispensing plastic fasteners of the type described above are designed to cut the opposing rails of a supply of ladder stock at equidistant intervals to generate a plurality of individual plastic fasteners. The specific fixed distance, or spacing, between successive cuts in the rails of the ladder stock (i.e., the length of the cross-bar of each dispensed plastic fastener) is commonly referred to in the art as the pitch in which the device operates. As can be appreciated, each fastener dispensing device is typically designed to sever and eject plastic fasteners from a supply of ladder stock at a fixed pitch (e.g., at a pitch of ¼ of an inch).
Preferably, plastic fastener dispensing devices of the type described above are designed to sever the rails of the supply of ladder stock at the approximate midpoint between successive filaments. In this manner, each dispensed fastener is ensured of having H-type configuration, with each end of its thin filament secured to the approximate midpoint of an associated cross-bar.
However, it has been found that conventional plastic fastener dispensing devices often fail to sever the rails of the supply of ladder stock at the approximate midpoint between successive filaments. This failure to properly sever the rails of the supply of ladder stock at the approximate midpoint between successive filaments can be caused by, inter alia, manufacturing tolerances in the thickness of the rails and filaments of the ladder stock which, in turn, can create lag, or rubbing, of the ladder stock within feed tracks in the fastener dispensing device. The lag created between the ladder stock and the fastener dispensing device precludes the feed mechanism for the device from adequately advancing the lowermost fastener in the ladder stock to the appropriate stop position within the device prior to the cutting process. Because the ladder stock is inadequately advanced by the feed mechanism, the severing process cuts the rails of the ladder stock at a location other than at the midpoint between successive fasteners. As a result, the device will dispense plastic fasteners which fail to have each end of its filament accurately bisect a corresponding cross-bar, thereby compromising its ability to generate fasteners which have the optimal H-type configuration.
Accordingly, it is well-known for fastener dispensing devices to provide for both internal (i.e., factory set) and external (i.e., operator accessible) fine tune (i.e., micro) adjustments to its feed mechanism. Specifically, during the assembly of such a device, the manufacturer preferably calibrates the internal fine tune adjustment to its feed mechanism such that a supply of ladder stock will properly align within the device prior to the severing process. With the internal fine tune adjustment optimized for a supply of ladder stock having a particular pitch, a protective casing is mounted onto a support plate so as to enclose the majority of the mechanical components for the device (e.g., the internal fine tune adjustments). The device is then shipped to the customer for use. However, if the customer still finds that the feed mechanism for the device is not optimized to sever the rails of the ladder stock at the midpoint between successive filaments, the customer is allowed to further fine tune the feed mechanism by means of an additional adjustment means which is externally accessible. Similar to the internal fine tune adjustment, the external fine tune adjustment for the device can be used to ensure that the relative stop position of the lowermost fastener in the ladder stock prior to the severing process is such that the approximate midpoint between successive filaments is aligned directly with the sharpened edge of each knife blade for the severing mechanism.
Although well known and widely used in commerce, fastener dispensing devices which include internal and external fine tune adjustment means to its feed mechanism have been found to suffer from a notable drawback. Specifically, it has been found that the feed mechanism for such a device is typically factory-set to its optimal position (i.e., using its internal adjustment means). However, inexperienced users often introduce misalignment into the feed mechanism by manipulating its external adjustment means. As can be appreciated, the external adjustment means for calibrating the feed mechanism is extremely sensitive and requires a certain level of precision which is typically found with only the more experienced and methodical users. As a result, it has been found that, more often than not, the presence of an external adjustment means causes the user to introduce misalignment into the feed mechanism which is not present upon completion of its manufacture, which is highly undesirable.